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The replacement of Portland cement, with a combination of calcined clay (CC), limestone and gypsum provides a sustainable and cost-effective solution along with promising mechanical properties compared to ordinary Portland cement. However, the utilization of calcined clay has a negative impact on the workability of the blended cement, and superplasticizers are commonly added to the mix. Unfortunately, the interactions between superplasticizers and calcined clays are less known. Clays can be composed of various minerals (kaolinite, smectite, illite, etc.) which, in their dehydroxylated form, can all interact differently with polycarboxylate ether (PCE), altering the fresh concrete properties. Two types of CC with different mineral compositions (illitic and kaolinite clays) were investigated. The influence of CC replacement (0–30%) in Portland cement binder was studied with respect to the dispersing ability of available PCEs. The rheological properties of CC-cement blends in pastes with different PCEs were investigated using a rotational rheometer and mini-slump flow tests to understand the effect of the type of CC and the PCEs on the rheological properties of CC-cement paste. Adsorption measurements were made by total organic carbon (TOC). In addition, isothermal calorimetry was used to study the hydration reaction of cement when CC and PCEs are present. Overall data signify that PCEs are efficient to improve workability of OPC-CC blends, but that the use of kaolinite CC will negatively influence the required dosage of PCE, while illitic CC has less influence.

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Elucidating Interaction Mechanism Between Various Clay Minerals and Superplasticizers in Cementitious Binders

  • 会议论文

  • 发表日期：

    2025年

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  • Ojas Chaudhari,
  • Gilles Plusquellec,
  • Emilie L’Hôpital,
  • Urs Mueller

摘要

The replacement of Portland cement, with a combination of calcined clay (CC), limestone and gypsum provides a sustainable and cost-effective solution along with promising mechanical properties compared to ordinary Portland cement. However, the utilization of calcined clay has a negative impact on the workability of the blended cement, and superplasticizers are commonly added to the mix. Unfortunately, the interactions between superplasticizers and calcined clays are less known. Clays can be composed of various minerals (kaolinite, smectite, illite, etc.) which, in their dehydroxylated form, can all interact differently with polycarboxylate ether (PCE), altering the fresh concrete properties. Two types of CC with different mineral compositions (illitic and kaolinite clays) were investigated. The influence of CC replacement (0–30%) in Portland cement binder was studied with respect to the dispersing ability of available PCEs. The rheological properties of CC-cement blends in pastes with different PCEs were investigated using a rotational rheometer and mini-slump flow tests to understand the effect of the type of CC and the PCEs on the rheological properties of CC-cement paste. Adsorption measurements were made by total organic carbon (TOC). In addition, isothermal calorimetry was used to study the hydration reaction of cement when CC and PCEs are present. Overall data signify that PCEs are efficient to improve workability of OPC-CC blends, but that the use of kaolinite CC will negatively influence the required dosage of PCE, while illitic CC has less influence.